For enabling the use in the nighttime or dark places, illuminating an operation key or an operation panel of portable electronic equipment such as a mobile telephone, a personal digital assistant (PDA), or a calculator is essential. On the other hand, such portable electronic equipment preferably consumes less power for illuminating an operation key so as to prevent battery depletion. For such reasons, the use of a light-emitting diode (LED) as an illumination source is proposed (Patent documents 1 and 2). These documents disclose devices having a structure in which one LED is placed for each switch.
However, there is a problem in that the above devices require a number of LEDs, consuming large amounts of power. Furthermore, an LED is placed under each switch, so that there also is a problem of the above devices having a large thickness, which makes it difficult to downsize them.    Patent document 1: JP 07-10701 Y    Patent document 2: JP 06-36162 Y